The present invention relates to a polymer electrolyte fuel cell, and a method for manufacturing the same.
The electrode of a polymer electrolyte fuel cell is generally manufactured by applying a carbon powder with a noble metal carried thereon (a catalyst powder) on a porous conductive base material. Specifically, first, a catalyst powder is dispersed in an organic solvent such as isopropyl alcohol to prepare an ink. Then, the obtained ink is applied on the base material by using a screen printing method or a transfer method to form a catalyst layer. Alternatively, there is another method in which a slurry containing a catalyst powder is applied on a resin sheet by using a doctor blade method or the like, to form a sheet of the catalyst powder.
With the foregoing methods, a pore forming agent is previously added to the ink. A catalyst layer containing the pore forming agent is then formed. Thereafter, the electrode is calcined to form micropores in the catalyst layer, thereby ensuring gas diffusion within the entire electrode. Further, the water repellence of the electrode can be enhanced by allowing the ink to contain a carbon powder with polytetrafluoroethylene (PTFE) carried thereon.
The electrode thus manufactured is joined to a polymer electrolyte membrane by hot pressing or the like, resulting in a membrane electrode assembly (MEA).
As described above, a process for removing the pore forming agent from the catalyst layer is required in obtaining an electrode by conventional methods. Specifically, a process of calcining or washing the electrode is required. Therefore, the conventional process of manufacturing the electrode is complicated.
Further, it is considered that a catalyst layer is preferably formed by directly applying the catalyst powder to the polymer electrolyte membrane from the viewpoint of an increase in electrode reaction area.
However, it is very difficult to form a catalyst layer directly on the polymer electrolyte membrane by a printing method or the like, from the viewpoints of swelling property of the polymer electrolyte membrane and difficulty in the fixation of the polymer electrolyte membrane to the printing machine.
The present invention relates to a polymer electrolyte fuel cell comprising a pair of electrodes, a polymer electrolyte membrane interposed between the pair of the electrodes, a first conductive separator having a channel for supplying an oxidant gas to one of the electrodes therethrough, and a second conductive separator having a channel for supplying a fuel gas to the other of the electrodes therethrough, wherein at least one of the electrodes comprises a porous conductive base material and a porous catalyst layer formed on a surface of the polymer electrolyte membrane. The first or second separator includes a separator having a channel for supplying an oxidant gas to one of a pair of electrodes on one side and a channel for supplying a fuel gas to one of other pair of electrodes on the other side.
The porous catalyst layer is preferably formed by spraying an ink containing a catalyst powder dispersed therein onto a surface of the polymer electrolyte membrane.
The catalyst powder herein denotes, for example, a carbon powder with a noble metal carried thereon.
Further, the present invention relates to a polymer electrolyte fuel cell comprising a pair of electrodes, a polymer electrolyte membrane interposed between the pair of the electrodes, a first conductive separator having a channel for supplying an oxidant gas to one of the electrodes therethrough, and a second conductive separator having a channel for supplying a fuel gas to the other of the electrodes therethrough, wherein at least one of the electrodes comprises a porous conductive base material and a porous catalyst layer formed on a surface of the porous conductive base material, the porous catalyst layer facing the polymer electrolyte membrane.
The porous catalyst layer is preferably formed by spraying an ink containing a catalyst powder dispersed therein onto a surface of the porous conductive base material.
Further, the present invention relates to a method for manufacturing a polymer electrolyte fuel cell comprising a step of obtaining an electrode by forming a porous catalyst layer by spraying an ink containing a catalyst powder dispersed therein onto a surface of a polymer electrolyte membrane or a porous conductive base material.
The ink is preferably the one containing a carbon powder with a noble metal carried thereon, the one containing a carbon powder with a noble metal carried thereon and a polymer electrolyte, or the one containing a carbon powder with a noble metal carried thereon, a polymer electrolyte, and a water repellent-treated carbon powder. The water repellent treatment may be conducted by using a fluorocarbon resin such as polytetrafluoroethylene (PTFE) or the like.